Evaluation of the Applicability of Iron Oxide-modified Lignin as a Stabilizer for Arsenic-contaminated Soil

This study evaluated the potential of iron oxide-modified lignin as a stabilizing agent for arsenic-contaminated soil. It also aimed to identify optimal synthesis ratios of iron oxide and lignin, determine appropriate mixing proportions, evaluate stabilization efficiency, and elucidate the stabilization mechanisms. Four stabilizers—LnFe25, LnFe50, LnFe75, and LnFe100—were synthesized by incorporating 25, 50, 75, and 100 grams of iron oxide into 20 grams of lignin, respectively. Batch stirring experiments revealed that while lignin alone increased arsenic mobility, iron-modified lignin significantly reduced arsenic leaching, confirming its stabilization efficacy. The optimal stabilization conditions were found with LnFe50 at a 5% mixing ratio, offering a favorable balance between effectiveness and economic viability. To assess stabilization performance, the toxicity characteristic leaching procedure, synthetic precipitation leaching procedure, and Wenzel tests were employed. The results demonstrated a marked reduction in arsenic leaching when using iron oxide-modified lignin compared to lignin alone. Mechanistic investigations through X-ray diffraction and scanning electron microscopy revealed that arsenic strongly adsorbs to the iron oxide component of the stabilizer, primarily through surface chemical interactions. These findings confirmed that the iron oxide-modified lignin stabilizer prevents arsenic from penetrating the iron oxide crystal structure, forming stable surface complexes instead. In conclusion, iron oxide-modified lignin presents a promising and sustainable solution for stabilizing arsenic-contaminated soil, providing an environmentally effective approach using waste materials for remediation.